How does the sensitivity for blockade by a LA compare regarding the following types of fibres?

• Myelinated fibres with unmyelinated fibres

Smaller and myelinated fibers easier blocked than larger and unmyelinated fibers therefore these myelinated fibres are more sensitive to local anaesthetics block.

• Pressure/touch nerves with the dorsal nerves that transmit pain impulses?

Blocking A-type fibres influences proprioception, touch, pressure and motor fibres. However, these fibres are blocked last by local anaesthetics and are therefore not as sensitive to local anaesthetics.

• Make a list of the effects of LA on other tissues.

Heart: Acts as a class 1 anti-arhythmic drug

Skeletal Muscle: weak blocking action of no clinical application

Cocaine: elevates mood and influences the catecholamine mediated neurotransmission(inhibits NA reuptake)

• What is the basis for the selection of a LA?
  • the type of procedure
  • the type of tissue that the drug must act on
  • the duration of the numbing effect that is required in that tissue.

• Why are LA solutions sometimes saturated with CO₂?

CO₂ acts as a buffer which reduces the pain of the injection and assists in a faster onset of action for the drug by increasing the effective concentration of the non-ionized form.

• Which of the LA are typically used for surface anaesthesia?

             Benzocaine, Cocaine and Oxybuprocaine

Brand, L. 2021. Local Anaesthetics. SU. 6 [PowerPoint Presentation]. Unpublished Lecture Notes on eFundi, FKLG 312. Potchefstroom, NWU.

Katzung, B.G. 2018. Basic and Clinical Pharmacology. 14^th ed. United States of America: McGraw-Hill Education